Integration of Support Structure and Turbine Design – Final Results of WP4-Task4.1 on Offshore Support Structures of the EU Upwind Project

摘要

For current offshore wind farms, monopiles are by far the most popularsupport structure type. However, for deeper water and/or largerturbines, the fatigue loading is becoming critical and the monopiledimensions are exceeding the current economical feasibility. Thereforethe paper focuses on an integrated optimization process for a 5MWoffshore wind turbine design on a monopile. The chosen site with 25mwater depth is considered to be challenging for such a large and heavyturbine type. The approach presented in this paper is to integrate anoptimization for load mitigation in the design process of offshoresupport structures.A reference design of the support structure is made following aconventional design approach and using data from measurements at asite in the Dutch sector of the North Sea. The focus is on the reductionof the dominant hydrodynamic loads on the support structure. Theimplemented load mitigation concept leads to significant reductions inloading, allowing considerable material savings and therefore a morecost-effective structural design. Undesired side effects, such asincreased wear of turbine components are unlikely as other systemloadings and characteristics remain within an acceptable range. Even ifsome of the rotor-nacelle-assembly loads are slightly increased by theapplied controller, the increases are low and probably still within themargins of the type-class fatigue loads. Furthermore a significantincrease in energy output could be obtained by applying an extendedcut-out range.